While not limited thereto, the present invention is particularly adapted for use with an atmospheric hazard sampling pump used to detect concentrations of harmful dust or gas in coal mines and other locations where the atmosphere may contain harmful constituents. A pump of this type must provide the necessary airflow for identifying atmospheric hazards with colorimetric or charcoal detector tubes. At the same time, it must be small enough and light enough to fit into a shirt pocket or clip onto the belt of a mine employee. The drive motor for the pump must be battery-powered and should incorporate a speed control system for minimizing speed fluctuations due to varying pneumatic loads and/or changing battery voltage.